Solar air warmer for ASHP

[Piwoslaw]

Originally Posted by Student 07

It would be better to store the heat when the ASHP isn’t running and use the heat when the ASHP needs it. For example a solar green house.

Your train of thought is correct, but you need to take one more step: Instead of storing extra heat in larger volumes of air, store it in a larger mass. Stones, bricks, sand, water, for example, or a phase-change material would be better. Using more mass instead of volume requires much less space and reduces losses. And is probably cheaper than building a 10'x10'x10' greenhouse

But even without lots of storage capacity, an ASHP with a prewarmer will still be more efficient than one without (as long as the intake isn't restricted), even if it's only by a few watts per minute.

[Xringer]

We have discussed the 'solar greenhouse' feeding an ASHP before around here..
I think it's a good idea. IRRC, My specs for the greenhouse was to make it long as possible, (E to W)
all glass on the South side, dark (and insulated) on the North side.
With some dark thermal mass on the inside north wall, with an insulated floor.
Insure that any light coming in would not be reflected back outdoors..

The mini-split ODU would be wall-mounted on one end, with the air input vents at the far end of the greenhouse.
The ODU would interface with the end wall so that outdoor air would not leak
around the sides of the unit, but be drawn from the far end of the greenhouse.

GreenHouse Mode would be very useful on sunny winter days (like today),
but in summer, some roof (heat-dump) vents would be needed,
plus some air-input vents adjacent to the ODU.
(To defeat the GreenHouse effect while trying to cool the house)!


Right now, the sun had made the outdoor air temperature shoot up to 40F.
So, my ASHPs are running less power, because of solar heat gain..
(Less power=less air flow over the ODU coils).

I would imagine, my proposed 32'x8'(?) greenhouse would be pretty
dang warm inside, even with a little 40F air being pulled into one end..

If it had double pane glass too?? Haha!

[Leoncondor]

What about such concept?
Annualized geo solar - Wikipedia, the free encyclopedia

PS.: Hope it will be of some use

[Piwoslaw]

Welcome to ER, Leoncondor

Originally Posted by Leoncondor

What about such concept?
Annualized geo solar - Wikipedia, the free encyclopedia

That's sort of what this is about, only on a much smaller scale: Instead of storing months of solar heat, the ASHP's prewarmer would store only a few minutes of hours of it. It all depends on size.

[eco_fred]

what you guys need is the sun
i think the best sulution and most stable solution is water / water heat pumps
because they have a stable tempr.
To encrease the cop you need heat on the evaporator a good superheat and good subcooling of the liquid in the airconditioner or hp.

[MN Renovator]

Originally Posted by Xringer

GreenHouse Mode would be very useful on sunny winter days (like today),
but in summer, some roof (heat-dump) vents would be needed,
plus some air-input vents adjacent to the ODU.
(To defeat the GreenHouse effect while trying to cool the house)!

{image}

Right now, the sun had made the outdoor air temperature shoot up to 40F.
So, my ASHPs are running less power, because of solar heat gain..
(Less power=less air flow over the ODU coils).

I would imagine, my proposed 32'x8'(?) greenhouse would be pretty
dang warm inside, even with a little 40F air being pulled into one end..

If it had double pane glass too?? Haha!

Your ASHP runs with less power because it is a variable speed compressor moreso than less air flowing over the coils. When less capacity is needed your unit steps down. Supplying it with hotter air will allow it to put out more heat for the same amount of power which will cause it to step down to a lower the heat its making or even shut off sooner. Don't forget solar heat gain is reducing your houses need for heating too so the heat pump runs less and at less power to keep up too, at least until your wife gets warm and wants to cool off the house a bit with the open window thing.

With the air flow and solar heat production, I think double pane glass wouldn't make enough difference. If it was scrap glass that was free, sure why not, but it seems there is tons of free scrap glass on Craigslist if you search the free section for glass. I've been looking for the perfect size to mostly utilize a 4x8 sheet of plywood to create a solar air heater that pumps hot air directly into my house since I don't have an ASHP(at least not yet) but then again my furnace this winter has been running almost exclusively at night for most of December and hasn't powered on since 12/24 but it will tonight because today is a cloudy day and the low is 9 degrees, last week was much warmer though high and low for the week 49.6f and 19.4f average 31.8f but all week we got lucky with cloudless sunny days almost every day.

I'm wondering how to swing that with an ASHP in a well insulated and air sealed house, I'm not about to add loads of rocks to the house but I'm thinking to add jugs of water in the most sun exposed areas of that house to absorb the day heat and then the sun-enhanced air source heat pump efficiency could be used to heat the house with a set back opposite of what I do now with the house warmer during the day than at night? This probably won't work well for an owl like me in weather like what we've had recently but it would help when we actually get a cold December or in January when the heat actually runs during the day.

[Leoncondor]

"The collector could also have a bit of thermal mass, which would store some heat if the sun is shining while the HP is off."

OK, what about storing thermal mass in some kind of solar pond, for such purpose pond could be small one, but well insulated.

What can a solar pond be used for?

generating heat
generating electricity
thermal energy storage

Solar Pond

http://www.google.pl/url?sa=t&rct=j&...XtZwDg&cad=rja

[Daox]

Then you pretty much have a solar hot water setup. They're great for heating purposes, just more complex/costly than an air panel.

[frankwest12345]

I have seen some all-in-one heat pump (air to air) designs that sit inside the house and just have a couple of large vents on the outside wall, there is even one with an inverter built-in but expensive at £1500... these are pregassed and have no external connections as they do not have an external unit so are ideal for DIY fitment and the inverter unit is rated down to minus 15 centigrade so great for the UK.

Because the input is just a five inch vent that comes out on the external wall it would seem ideal to match to a solar wall design but as mentioned airflow is a critical factor but maybe you can have an insulated backplate full of copper tubing and water/glycol mixture to retain some more heat. I have a south facing wall and in winter the sun is low enough to make wall mounting perfect.

Because you get three to four times as much energy out of a heat pump as you put in this is surely more efficient than using a thermal solar panel or evacuated tubes to directly heat a radiator?